The fuel provided to engines, such as auxiliary power units (APUs), which are typically used to supply electrical or pneumatic power to various aircraft systems, is generally heated by means of a Fuel Oil Heat Exchanger (FOHE). The fuel is indeed circulated in the FOHE, where the heat generated by the engine's oil system is transferred to the fuel.
Excessive or insufficient heating can lead to undesirable effects, such as fuel system fire safety impacts, fuel nozzle coking, or fuel icing (e.g. filter clogging) conditions. In order to monitor the temperature downstream of the outlet (e.g. the health) of the FOHE, existing systems make use of a fuel temperature sensor or a fuel temperature switch. When a fuel temperature switch is used to monitor the health of the FOHE, only a notification as to whether the fuel temperature is outside of a predetermined range is provided. This information is however insufficient to determine if the health of the FOHE or if the fuel temperature switch itself is at fault.
There is therefore a need for an improved system and method for detection of heat exchanger failure.